Manufacture of ferrochromium



PATENT OFFICE.

UNITED STATES ILLIAM LAWRENCE TURNER,

or arnnas'ronn, ENGLAND.

MANUFACTUR or rnnnocnaomrum.

Iomlwlng.

To all whom it may concern:

Be it known that 1, WILLIAM LAWRENCE Turner, a subject of the King of England and residin at Atherstone, in the'county of Warwick, ngland, have invented Improvements in the Manufacture of Ferrochromium, of which the tion.

This invention has reference to the production of the metallic alloy known as carbon free ferrochromium, process known as the alumino-thermic process which is usually sold and used in metal-' lurgy for the manufacture of, ferro alloys or steels; and this invention has for its object primarily, to produce such ferro-chromium at a relatively low cost, and also to obviate certain disadvantages and defects of the process manufacture, which are inherent in it.

The actual manufacture of carbon free ferro-chromium from chromium iron ore by the alumino-thermic process, as hitherto carried out, has been accompanied by many difficulties, by reason partly of the refractory nature of this ore, intensified by the inclusion in it of considerable percentages of magnesia, alumina, lime, and other more or less inert matters, which do not necessarily take art in the reaction; and furthermore, it is the efficiency of the when great care is following is a specificareduction, is poor, even taken in a variety of ways which are ado ted to make the reaction take place at all. or the more satisfactory carrying out of the reaction referred to, it

' has been proposed to use with chrome iron application of r a yield of thechromium 65' ore a quantity of chromium oxid, and also to pre-heat, to a moderate degree, the thermic mixture, for the! purpose of generally assisting the reaction.

Now according to and for the purposes of this invention, a proportion of bichromate or chromate of potassium (or bi-chromate or chromate of sodium) is mixed with the of chromium chemically e uivalent mixture iron ore, an aluminium or equivalent reducing medium. I find that bythe use and this bi-chromate or chromate in the chemical equivalent mixture, the reaction is caused to take place readily and satisfactorily, increasing the efliciency and from the chrome iron the chromium of the while in. addition,

is also ylelded up bi-chromate or chromate, in the alloy produced.

Specification of Letters latent.

produced by the heretofore employed, for its own that the yield of chromium, or-

Patented July 13, 1920.

Application filed Ianuary 7, 1918. Serial No. 210,697.

The alumino-ther'mic mixture may be moderately preheated, for the purpose of assisting the reaction and increasing the efficiency.

Regarding the carrying out of this invention of the roduction of carbon free ferrochromium rom chromium iron ore by the alumino-thermic process, the following is an example :-In an. alumino-thermic mixture 1f to 120 parts by weight of chromium ore (the latter containing about 50% of sesquioxid of chromium) there be added 24 parts of bi-chromate of potash, together with the necessary equivalent quantity of aluminium or other reducing metal, and the mixture be heated to a dull red heat, and then set into reaction in the well known way, the productthe carbon free ferro-chromium-will contain from 70% to 75% of chromium; the yield of chromium from the-chromium containing material in the alumino-thermic mixture being in the neighborhood of 85%. While this result may be obtained by the use of the percentages referred to, by employing other proportions, having regard to the nature of the particular ore being worked, satisfactory yields may be secured.

The actual reaction which takes place as a result of the addition of bichromate of soda (or potash) to the .mixture of chrome ore and aluminum is largely a matter of surmise, but I hold that the available oxygen is all combined with the aluminum to form A1 0 and thus there will be a large amount of additional heat imparted tot-the reaction, which actually seems to be borne out in practice. By this I mean to say that the sodium oxid is decomposed'by the aluminum with liberation of sodium in the metallic form, and the latter in turn acts as a reducing agent in the aluminothermic reaction. The chromium reduced from the bichromate passes, as desired, into the regulus formed by the reaction of the aluminum with the chrome iron ore.

To simplify the matter it may be well to regard the bichromate as a compound of chromic acid and oxid of sodium and to treat I The first reaction is complete, while the second is only partially so as owing to dense from the reacting fumes of soda arising as having the chemical mass, it is obvious that the atmosphere.

sodium liberated maybe regarded formula N 21 0. C10 and assuming that the N a O is Vola tilized in the reaction, there will remain three heat producing each atom of chromium, whereby the heat units developed for available use is great.

at is claimed.is:-

l. The herein described process which consists in mixing a chromate of the alkali met- ..weight of chromium iron owing to the fact thatatoms of oxygen to metal, e reacals, chromium iron ore and a reducin and heating the mass for effecting t tion.

2. The herein described process which consists in mixing substantially 120 parts by ore, 24; parts by weightof a bichromate of the alkali metals,

.and a chemically equivalent portion of a reducing metal, and heating the mass to effect the reaction.

3. The herein described process, which consists in preheating a thermic mixture containing a bichromate of the alkali metals and a reducing metal to cause chemical reaction 1 to be set up, and introducing into the mass a chromium iron ore in the 'resence of the heat and reaction and furt er heating the mass.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

, WILLlAM LAWRENCE TURN Witnesses:

A. M. HANNAY, SOMERVILLE GoonALL. 

